The semiconductor industry has moved to using copper in various aspects of semiconductor devices due to certain advantages of copper over other metals. One advantage is that copper has a lower resistivity than aluminum, for instance. As a result, copper circuitry suffers less from resistance-capacitance (RC) delays. This makes copper systems faster. Further, copper has increased resistance to electromigration, thereby enabling smaller scaling of semiconductor devices. However, with increased use, certain problems particular to copper have become more prevalent. One such problem is that copper has a high diffusivity through dielectric and silicon materials on which the copper is deposited. This is especially the case for so-called low-K dielectric materials, which are coming into increasingly common usage. This is problematic because the presence of copper in these materials may be deleterious to these materials and lead to semiconductor device failure.
In conventional methodologies, a barrier material is typically deposited on the dielectric material between the copper layer and the dielectric (or silicon) material, thereby preventing the copper from diffusing into the dielectric or silicon material. Typically, tantalum (Ta) or titanium (Ti) based barrier materials (e.g., tantalum nitrides (TaN), tantalum silicon nitrides (TaSiN), or titanium nitrides (TiN)) are used as barrier layers for copper. Techniques such as atomic layer deposition (ALD) are often used to form the barrier layer. One problem with prior uses of tantalum nitride and other barrier layers, however, is that these barrier layers are poor wetting agents for the deposition of copper thereon which may cause numerous problems. For example, during deposition of a copper seed layer over these barrier layers, the seed layer may agglomerate and become discontinuous, which may prevent uniform deposition of a copper conductive material layer. Instead of a seed layer, a catalytic layer may be formed on the barrier layer so that an electroless plating process may be employed to form the copper layer. Similar to the copper seed layer, the catalytic layer may form discontinuously on the barrier layer, leading to formation of a less than satisfactory copper conductive layer. Thus, there is a need for an improved interconnect structure and method of depositing the interconnect structure.